My mum received a chain letter years ago, being the superstitious type, she went to pieces over it so I told her to pass it to me - that way she'd followed the instructions. Needless to say, I just ripped it up.
You shouldn't have to sign or forward anything you don't wish to. I really don't like the fact that people who have my email address think I would want to be a part of such things.
- Especially if it has a horrible/threatening message at the end.
Just delete it and think nothing else of it.
If you wish to help causes and charities then it should be done in your own time and on your terms. Not by force of a threatening letter.